Systems and methods for selecting a network access system

ABSTRACT

A system according to some embodiments of the invention includes (1) a component (e.g. ANDSF) that provides a cell selection rule to a UE and (2) a component (e.g. an access node) that provides the UE with information about the load in the cell currently utilized by the UE. This enables the UE to determine whether to leave the cell, which may be a 3GPP cell, and use a different cell, which may be a non-3GPP cell, by applying the cell selection rule in conjunction with its knowledge about the load of the cell.

This application is a continuation of application Ser. No. 12/487,267,filed on Jun. 18, 2009, which is incorporated by reference herein.

TECHNICAL FIELD

The present invention relates to communication networks. Particularaspects of the present invention relate to network access systemselection.

BACKGROUND

It is expected that network access systems of various kinds, especiallywireless network access systems (e.g. access nodes, such as basestations, of various types), will become increasingly ubiquitous.Accordingly, it is expected that mobile terminals (e.g. mobile phonesand other mobile terminals) will be configured to be able to communicatewith several different types of base stations, thereby providingflexibility to select the best type of base station to use for any givencommunication session. That is, it is expected that mobile terminals(a.k.a., user equipments (UEs)) will have multiple access interfaces.For example, in Long Term Evolution (LTE)/System Architecture Evolution(SAE) networks, also known as Evolved Packet System (EPS), multi-accessis a key element. This means that an EPS UE will often face a situationwhere it has to select which out of multiple available network accesssystems to use (i.e. the UE has to perform access selection).

To leverage the benefits of having these multiple access interfaces itis desirable to have mechanisms and procedures in place to ensure that amobile terminal uses its available access interfaces and network accesssystems as efficiently as possible. In this context, the perspectives ofboth the user of the mobile terminal and the operator of the networkaccess system should preferably be considered. Accordingly, a newfunctional entity referred to as Access Network Discovery and SelectionFunction (ANDSF) has been introduced into the Third GenerationPartnership Project (3GPP) network architecture, and correspondingfunctionality has been introduced in the UE (sometimes referred to asueANDSF). The principle of ANDSF based access selection is that theANDSF supplies rules/instructions to a UE, and the UE applies theserules/policies to its current contextual situation to arrive at anaccess selection result. That is, the ANDSF controls access selectionindirectly and on a non-real-time scale. Hence, the current ANDSF accessselection mechanism is not well suited to provide, for example, loadbalancing functionality.

What is desired are improved systems and methods for selecting a networkaccess system. Henceforth the terms “access selection” and “cellselection” will be used as equivalents.

SUMMARY

A system according to some embodiments of the invention includes (1) acomponent (e.g. ANDSF) that provides a cell selection rule to a UE and(2) a component (e.g. an access node) that provides the UE withinformation about the load in the cell currently utilized by the UE.This enables the UE to determine whether to leave the cell, which may bea 3GPP cell (i.e. a cell wherein 3GPP radio access technology is used,such as LTE, WCDMA, HSPA, Global System for Mobile communication (GSM),General Packet Radio Service (GPRS) or Enhanced Data rates for GSMEvolution (EDGE)), and use a different cell, which may be a non-3GPPcell, by applying the cell selection rule in conjunction with itsknowledge about the load of the cell. An advantage of this aspect of theinvention is that extra-3GPP load balancing can be achieved while thegeneral principle for ANDSF based access selection is preserved. Thatis, the ANDSF provides the cell selection rules, while the UE monitorsits environment and applies the rules. In some embodiments, the accessnode can provide the UE with information about the load by transmittinga cell preference indicator (CPI) value. The transmission may be abroadcast or unicast transmission. In some embodiments, timers areintroduced to govern how long a load-triggered access selection decisionis valid in a UE, both after decisions to move and not to move.

In one particular aspect, the invention provides a UE load balancingmethod. In some embodiments, the method begins with the UE receiving amessage comprising a cell selection rule. Next, the UE receives a cellpreference indicator (CPI) value transmitted from an access node (e.g. a3GPP access node). The CPI value is associated with the cell currentlyutilized by the UE. Next, the UE uses the cell selection rule inconjunction with the CPI value to determine whether to continueutilizing the cell or to move to a second cell (e.g. a cell serviced bya non-3GPP access node). In some embodiments, the CPI value is a binaryload indicator value that indicates whether the cell is considered to beloaded or unloaded. In other embodiments, the CPI value is a loadindicator value that indicates one of three or more cell load levels. Instill other embodiments, the CPI value indicates whether, or the degreeto which, the first cell is suitable for access. In some embodiments,the step of using the cell selection rule to determine whether toutilize the second cell includes generating a random or pseudo-randomnumber and comparing the generated number with a value that is afunction of the CPI value. The cell selection rule may specify acondition, and the step of using the cell selection rule in conjunctionwith the CPI value to determine whether to utilize the second cellcomprises using the CPI value to determine whether the condition istrue.

In another aspect, the invention provides method for load balancing in acommunication network. The method may begin by transmitting to a UE amessage comprising a cell selection rule. Next, a message comprising acell preference indicator (CPI) value that is associated with a firstcell is created by an access node. This message is then transmitted tothe UE from the access node. Advantageously, the UE is configured to usethe received cell selection rule in conjunction with the received CPIvalue to determine whether to utilize the first cell or a second cell.In some embodiments, the step of transmitting the message containing theCPI value comprises transmitting the message on a broadcast channel(BCH) or a downlink shared channel (DL-SCH). In other embodiments, thestep of transmitting the message containing the CPI value comprisesunicasting the message to the UE. In some embodiments, prior tounicasting the CPI value to the UE, the access node determines whetherthe UE is transmitting and/or receiving primarily traffic with lowcapacity demands. If so, the access node will unicast the CPI value tothe UE, otherwise the access node will not unicast the CPI value to theUE. In some embodiments, the access node determines the load on thefirst cell and determines a target number of UEs based on the determinedload. Next, the access node selects not more than the target number ofUEs and transmits a CPI value to each of the selected UEs.

In another aspect, the present invention provides an improved UE. Theimproved UE includes (1) a transmit and receive circuit operable to (a)receive a cell selection rule and (b) receive, from an access node, acell preference indicator (CPI) value associated with a cell. Theimproved UE also includes a data processing system configured to use thecell selection rule in conjunction with the received CPI value todetermine whether to utilize the cell or a different cell.

In another aspect, the present invention provides an improved accessnode. The improved access node includes (1) a transmit and receivecircuit operable to transmit and receive data and (2) a data processingsystem. Advantageously, the data processing system is configured to (a)determine the load of a cell serviced by the access node, (b) set a cellpreference indicator (CPI) value based on the determined cell load, (c)generate a message comprising the CPI value, and (d) cause the transmitand receive circuit to transmit the message to one or more UEs inwireless communication with the access node.

The above and other aspects and embodiments are described below withreference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated herein and form partof the specification, illustrate various embodiments of the presentinvention and, together with the description, further serve to explainthe principles of the invention and to enable a person skilled in thepertinent art to make and use the invention. In the drawings, likereference numbers indicate identical or functionally similar elements.

FIG. 1 illustrates a communication system according to some embodimentsof the invention.

FIG. 2 is a flow chart illustrating a process according to someembodiments of the invention.

FIG. 3 is a flow chart illustrating a process according to someembodiments of the invention.

FIG. 4 is a flow chart illustrating a process according to someembodiments of the invention.

FIG. 5 is a functional block diagram of an access node according to someembodiments of the invention.

FIG. 6 is a functional block diagram of a UE according to someembodiments of the invention.

DETAILED DESCRIPTION

A term/concept which is relevant for the following detailed descriptionof the invention is “extra-3GPP load balancing”. In this document“extra-3GPP load balancing” refers to load balancing between the domainof 3GPP accesses (i.e. the accesses using access technologies specifiedby 3GPP, e.g. LTE, WCDMA, HSPA, GSM, GPRS and/or EDGE, possibly alsoincluding CDMA2000® which is specified by 3GPP2) and the domain ofnon-3GPP accesses (i.e. accesses using access technologies which are notspecified by 3GPP). Hence, extra-3GPP load balancing mechanisms are usede.g. to achieve good load balance between a cell serviced by an accessnode using 3GPP access technology and a cell serviced by an access nodeusing non-3GPP access technology. Potentially, extra-3GPP load balancingmechanisms could also be used for balancing the load between two cellsserviced by access node(s) using non-3GPP access technologies, butextra-3GPP load balancing mechanisms are typically not used for loadbalancing between cells serviced by access node(s) using 3GPP accesstechnologies.

Referring now to FIG. 1, FIG. 1 illustrates an exemplary communicationsystem 100 according to some embodiments of the invention. As shown inFIG. 1, communication system 100 includes multiple access nodes 104(e.g. access node 104 a and access node 104 b). Each access node 104 mayprovide a number of UEs 102 with access to network 110. For example,access node 104 a may provide UEs within coverage area (i.e. cell) 105 a(i.e., UEs 102 a-102 d) with access to network 110, while access node104 b may provide UEs within coverage area (i.e. cell) 105 b (i.e., UEs102 b-102 c) with access to network 110. That is, access node 104 aserves cell 105 a and access node 104 b serves cell 105 b.

In some embodiments, access node 104 a may be of a different type thanaccess node 104 b. For example, access node 104 a may be a 3GPP accessnode (i.e. an access node using 3GPP access technology, e.g., an LTE,high speed packet access (HSPA), wideband code division multiple access(WCDMA), Global System for Mobile Communication (GSM), GSM Enhanced DataRates for GSM Evolution (EDGE) Radio Access Network (GERAN), or possibly3GPP2 CDMA2000® access node), while access node 104 b may be a non-3GPPaccess node (e.g., Worldwide Interoperability for Microwave Access(WiMAX), Wireless Local Area Network (WLAN), or other non-3GPP accessnode).

As also illustrated in FIG. 1, system 100 may include a server 106 thatprovides ANDSF functionality. That is, server 106 may be configured toprovide to UEs 102 one or more cell selection rules. Advantageously, atleast one access node (e.g., access node 104 a) is configured totransmit a cell preference indicator (CPI) value to one or more of UEs102 that are currently utilizing cell 105 a (e.g., UEs 102 a-102 b), andthe UEs receiving the CPI value are configured to use a cell selectionrule provided by server 106 in conjunction with the CPI value providedby access node 104 a to determine whether to continue “utilizing” cell105 a or utilize a different cell (e.g., cell 105 b). A UE “utilizes” acell by connecting to or camping on the access node 104 (or componentthereof) that serves the cell.

In some embodiments, the CPI value conveyed to the UEs may come indifferent variants with different properties. For example, in someembodiments, the CPI value is a binary load indicator value thatindicates whether a particular cell (e.g., the cell served by the accessnode that conveyed the CPI value) is loaded (e.g., highly loaded orcompletely loaded) or unloaded (e.g., completely unused or just lightlyused). In other embodiments, the CPI is a “nuanced” load indicator. Thatis, for example, the CPI is a value that indicates one of three or morecell load levels (e.g., low load, medium load, and high load).

Advantageously, by providing a UE 102 with knowledge about the load inthe cell the UE is currently utilizing, a network operator mayproactively control load-balancing by having the ANDSF server 106 conveyto the UE 102 a cell selection rule conditioned on the load of a cell.This way, the general principle for ANDSF based cell selection ispreserved with the ANDSF providing the cell selection rules while the UEmonitors contextual parameters (e.g., cell load, traffic type, etc.) andexecutes the cell selection rule using the contextual parameters asinput.

In some embodiments, a cell selection rule may instruct a UE 102 to, bydefault, utilize the available access node that has the highest capacityand bit-rate. In many cases, such an access node will be an LTE basestation. Hence, providing a UE 102 with information about the load inLTE cells so that the UE can move away from overloaded LTE cells andutilize non-3GPP cells will enable extra-3GPP load-balancing. In someembodiments, the task to inform a UE of a cell 105's load condition isplaced in the node that has the most readily available knowledge aboutthe load situation, which in most cases is the access node 104 thatserves the cell 105. In the LTE environment the access node 104 isreferred to as an evolved NodeB (eNB). In WCDMA/HSPA it may include aNode B, but the task to inform the UE of a cell's load in a WCDMA/HSPAnetwork may also be placed in a Radio Network Controller (RNC) nodecontrolling multiple Node Bs. That is, the access node 104 may include aNode B and RNC.

In other embodiments, the CPI may be used as a general indicator (asopposed to merely a load indicator) that indicates the degree to whichthe cell is suitable for access. For example, in some embodiments, theCPI may have only two states: (1) “allowed” and (2) “not allowed.” Anaccess node may set the CPI value to “not allowed” when the cell isloaded. That is, the access node may use the general CPI as a binaryload indicator. In addition, however, the access node may also set theCPI value to “not allowed” when, for example, the cell is taken out ofservice or when the network operator desires to save energy. Thus, inthis embodiment, while the CPI is a binary indicator it is more generalthan a simple binary load indicator. In other embodiments, the CPI mayhave three or more states (e.g. low, moderate, high). This is useful toachieve smooth load balancing (e.g. gradually decrease the number of UEsin the cell). This may be desired when the access node is being takenout of service, e.g. for maintenance or upgrades.

In other embodiments, the CPI value may be a probability value (or othervalue) that a UE uses in determining whether or not to use the cell forcamping or connected mode access. The CPI value transmitted to a UE atany particular time may reflect the load in the cell at that time or beused for other purposes as described above with respect to the generalindicator. In this embodiment, by adjusting the CPI value, it ispossible to regulate the fraction of UEs that choose to use the cell andthe fraction that select another cell.

There are a variety of ways in which an access node 104 may provide aCPI value to a set of one or more UEs 102. For example, the access nodemay broadcast the load indictor (i.e. transmit the load indicator sothat it can be received by any UE that is listening to the broadcast).Broadcasting the CPI value is an efficient way to simultaneously conveythe CPI value to all UEs in the cell (including both active and idleUEs). In some systems (e.g. LTE), one way to broadcast the CPI value isto include it with the system information that is repeatedly broadcastin the cell by the access node. For example, the CPI value may beincluded in the “MasterInformationBlock (MIB)” that is periodicallybroadcast using the Broadcast Channel (BCH). The LTE MIB currently has afield of 10 unused bits and one or more of these unused bits could beused to carry the CPI value. As another example, the CPI value may beincluded in one of the SystemInformationBlocks (SIBs) that istransmitted on the Downlink Shared Channel (DL-SCH) of LTE. The CPIvalue could also be placed in a “non-critical extension” of the“SystemInformation Message”, which is an open-ended mechanism forbackwards compatible extensions of the system information withparameters which may be skipped by UEs that cannot interpret theinformation, but it may also be included as a regular system informationparameter.

Another way the access node 104 may provide a CPI value to a set of UEsis to unicast the CPI value to each UE in the set (i.e. to send aseparate message to each UE with the UE as the dedicated receiver). Forexample, for each UE included in the set, the access node may transmitthe CPI value so that it is received only by the UE. A benefit of usingunicast instead of broadcast to convey the CPI value is that the accessnode can direct the CPI value to selected UEs. This allows the accessnode to, for example, send a CPI value indicating an overload conditiononly to those UEs that the access node has determined will suffer theleast from leaving the cell for an another cell (e.g. UEs transmittingand/or receiving primarily traffic with low capacity demands, such asbest-effort or low bit rate traffic). For unicast delivery, the CPIvalue may be included in a Radio Resource Control (RRC) message sentfrom the access node to the UE, or it may be included in a lower layerprotocol (e.g. Media Access Control layer) or in a higher layer.Additionally, other signaling mechanisms could be used, such assignaling over the Internet Protocol (IP) (e.g. OMA Device Management)or IEEE 802.21 based signaling mechanisms. The CPI value could be anoptional parameter in any unicast RRC message, but it could also beincluded in all unicast RRC messages or transmitted in a dedicatedmessage. Preferably, the access node “opportunistically” transmits theCPI value to the UE. For example, when the access node determines thatit should transmit a CPI value to a UE, the access node may not transmitthe CPI value immediately to the UE, but may wait until the access nodehas other data, e.g. RRC related data, to send to the UE and thentransmit to the UE the CPI value along with the other data.

Because the decision to move to the another cell is ultimatelycontrolled by a cell selection rule and because not all UEs in the cellmay have the possibility to move to a another cell (e.g. because theylack the appropriate interface or are out of coverage of the concernedaccess), it may be that not all the UEs that receive an overloadindication (e.g. a CPI value set to “loaded” or “not allowed”) will moveto the other cell and the access node cannot predict how large afraction of the UEs will move to the other cell. To compensate for this,the access node may choose to send the overload indication to more UEsthan the access node would actually want to leave the cell. This, ofcourse, may lead to more UEs leaving the cell than is desired. Apossible way around this problem is that the access node first sends theoverload indication to exactly the number of UEs it would like to movefrom the cell for optimal load-balancing and then wait and see whathappens. If not all the contacted UEs have left the cell after a certaintime, the access node may send the overload indication to additional UEsand so on. Another option is to send the overload indication to all UEsin the cell. When a suitable number of UEs has left the cell because ofthe signaled overload condition, the cell will not be overloaded anymoreand the access node can change the load indication to stop further UEsfrom leaving the cell for load-balancing reasons.

Referring now to FIG. 2, FIG. 2 is a flow chart illustrating a process200 according to some embodiments of the invention. Process 200 is aprocess performed by a UE (e.g., UE 102 a) that is utilizing aparticular cell (e.g. cell 105 a, which is serviced by access node 104a). Process 200 may begin in step 202, where UE 102 a receives a cellselection rule. UE 102 a may receive the cell selection rule from server106. UE 102 a may pull (e.g. request) the rule from server 106 or server106 may push (e.g. send unsolicitedly) the rule to UE 102 a. In step204, UE 102 a receives from access node 104 a a CPI value, which, asdiscussed above, may be broadcast or unicast. Next (step 206), UE 102 aexecutes the cell selection rule using the CPI value it most recentlyreceived from access node 104 a to determine whether it should continueutilizing cell 105 a or utilize another cell (e.g. cell 105 b).

In some embodiments, the cell selection rule specifies a condition.Accordingly, in some embodiments, UE 102 a executes the cell sectionrule by determining whether the condition is true. If UE 102 adetermines that the condition is true, then UE 102 a should perform aspecific action, which also may be specified by the cell selection rule.

An example cell section rule may be as follows: “condition=>CPIvalue=‘loaded’; action=>WiMAX, WLAN”. When UE 102 a executes this cellselection rule, UE 102 a will determine whether the condition is true(i.e. UE 102 a will determine whether the CPI value it received in step204 equals the value of “loaded”). If the condition is true, then UE 102a will perform the specified action. In this example, the action is todiscontinue utilizing the current cell and utilize a WiMAX cell if oneis available, otherwise utilize WLAN cell if one is available. Ifneither a WiMAX nor WLAN cell is available, the UE 102 a will continueutilizing the current cell. Accordingly, as illustrated, the action ofthe cell selection rule may specify a set (e.g. ordered list) of celltypes.

For illustration, Table 1 below illustrates other possible cell sectionrules.

TABLE 1 Cell Selection Rules Condition(s) Action(s) CPI value = ‘loaded’.AND. accessType = WiMAX, WLAN LTE .AND. serviceType = low bit rate orbest-effort randNum( ) < f(CPI value) WiMAX, WLAN randNum( ) < 0.6 .AND.CPI value = ‘loaded’ .AND. WiMAX, WLAN serviceType = low bit rate orbest-effort CPI value = ‘loaded’ WiMAX, WLAN CPI value = ‘not loaded’.AND. serviceType = low WiMAX bit rate

The first cell selection rule in Table 1 illustrates that the conditionmay include logic (e.g. binary logic). According to this rule, UE 102 awill discontinue utilizing the current cell if: (a) the CPI value is setto ‘loaded’, (b) the access node that UE 102 a is currently utilizing isan LTE access node (e.g. an eNB), (c) UE 102 a is primarily transmittingand/or receiving low bit rate or best-effort traffic, and (d) UE 102 ahas available to it a WiMAX or WLAN cell that it can utilize. The secondcell selection rule in Table 1 illustrates a probability based cellselection rule. When UE 102 a executes this cell selection rule, UE 102a will generate a random number (e.g. a pseudo-random number) andcompare the generated random number with a value that is a function f( )of the CPI value. In this example, if the generated random number isless than f(CPI value), then UE 102 a will perform the specified action.In some embodiments, f(CPI value)=CPI value×C, where C could be anyvalue. In other embodiments, f(CPI value)=CPI value raised to the powerof C. In embodiments where CPI value is a binary load indicator, thenf(CPI value) may equal X if CPI value=‘loaded,’ otherwise f(CPI value)may equal Y. The third cell selection rule is also a probability basedrule. Probability based cell selection rules allow simple control of UEor UE group behavior, while at the same time avoiding complex cellselection rules. The fourth cell selection rule illustrates that a cellselection rule may contain a set of conditions and a corresponding setof actions.

Referring back to FIG. 2, if UE 102 a determines based on the cellselection rule and the CPI value that it should continue utilizing cell105 a, then UE 102 a may set a timer to expire after some configurableamount of time or wait for a load balancing command from access node 104a (step 208). In response to the timer expiring (or in response toreceiving the load balancing command), UE 102 a again performs step 206.This feature of setting a timer forces UE 102 a to re-execute the cellselection rule at some later point in time. This is advantageous inembodiments where the cell selection rule is a probability based rulebecause, without such re-execution of the cell selection rule, the loadbalancing may be too rigid. For instance, in an cell overload situation,if an insufficient number UEs leave the cell, then this undesirablesituation may persist if the UEs' probability based cell sectiondecision was not reconsidered. Accordingly, a UE should start a timerafter a probability based decision to remain in the cell and when thetimer expires, this should trigger a new evaluation of the cellselection rule, which may or may not result in the UE moving to a newcell. The timer may be fixed (i.e. the same for all UEs), but randomtimers within a certain interval may result in a smoother load balancingoperation.

If UE 102 a determines based on the cell selection rule and the CPIvalue that it should discontinue utilizing cell 105 a, then UE 102 awill begin utilizing a new cell (e.g. cell 105 b) and may set a timer toexpire after some configurable amount of time (step 210). Uponexpiration of the timer, UE 102 a executes a cell selection rule (e.g.the one received in step 202 or a different rule) using a default CPIvalue as an input variable to determine whether to continue utilizingthe new cell (step 212). If UE 102 a determines based on the cellselection rule and the default CPI value that it should continueutilizing the new cell, then process 200 returns to step 210, otherwiseprocess 200 goes to step 213, where UE 102 a stops utilizing cell 105 band resumes utilizing cell 105 a. After step 213, process 200 proceedsto step 208. The timer is set in step 210 because UE 102 a's decision toleave cell 105 a and move to cell 105 b should not last forever. A timeris used to force UE 102 a to re-evaluate a cell selection rule becausewhen UE 102 a is utilizing cell 105 b it may have no knowledge of thestate of cell 105 a as access node 104 b may not have the means toprovide to UE 102 a information regarding the state of cell 105 a.Preferably, to avoid large groups of UEs returning to cell 105 a, thetimer may be set to a random value within a certain interval.

Referring now to FIG. 3, FIG. 3 is a flow chart illustrating a process300 according to some embodiments. Process 300 may be performed by a3GPP access node (e.g. access node 104 a). Process 300 may begin in step302, where access node 104 a determines the load of one of its cells.Next (step 304), access node 104 a sets a CPI value to a particularvalue (e.g. a value that is based on the determined load of the cell).For instance, if the CPI is a nuanced load indicator and access node 104determines that the load of the cell is normal, then access node 104 awould set the CPI value to “normal.” Next (step 306), access node 104 agenerates a message that includes the CPI value. As discussed above,access node 104 a may generate a MIB or SIB and include the CPI value inthe MIB or SIB. Next (step 308), access node 104 a broadcasts themessage containing the CPI value. In an LTE system, access node 104 amay broadcast the message using the Broadcast Channel (BCH) or maybroadcast the message using the Downlink Shared Channel (DL-SCH).

Referring now to FIG. 4, FIG. 4 is a flow chart illustrating a process400 according to some embodiments. Process 400 may be performed by a3GPP access node (e.g. access node 104 a). Process 400 may begin in step402, where access node 104 a determines the load of one of its cells.Next (step 404), access node 104 a sets a CPI value to a particularvalue (e.g. a value that is based on the determined load of the cell).Next (step 406), access node 104 a determines a target number (T) of UEsand sets a counter (i) equal to zero (0). The target number may be setto the number of UEs that access node 104 a would like to have moved toanother cell (or it may be set to a higher or lower number). In step408, access node 104 a obtains (e.g., receives or generates) dataintended for a UE. Next (step 410), access node 104 a determines whetherthe UE is a candidate UE for being moved to another cell. For example,in some embodiments a UE is a candidate UE if and only if it istransmitting and/or receiving primarily traffic with low capacitydemands (e.g. low bit rate traffic or best effort traffic). If the UE isnot a candidate, then access node 104 a will transmit to the UE the dataobtained in step 408 (step 412). After step 412, process 400 may returnto step 408. If the UE is a candidate, access node 104 a determineswhether the counter i equals the target number T. If i=/=T, then accessnode will increment i (step 414) and transmit to the UE a messagecontaining data obtained in step 408 and the CPI value set in step 404(step 416). Advantageously, each UE that receives a message containing aCPI value will execute a cell selection rule using the received CPIvalue. After step 416, process 400 may return to step 408. If i=T, thenaccess node 104 a will transmit to the UE the data received in step 408(step 418). After step 418, process 400 may return to step 402. Byimplementing this process, access node 104 can indirectly control theload in the cell because each candidate UE that receives the CPI valuewill, in response to receiving the CPI value, execute a cell selectionrule that if properly designed will cause the UE to move to another cellif the CPI value indicates that the cell is overloaded. Note that step410, determining whether the UE is a candidate for being moved toanother cell, may be performed before step 408. In such case, the accessnode first determines that a UE is a candidate UE and thenopportunistically waits for data to send to the UE, so that steps 414and 416 can be performed on condition that i=/=T.

Referring now to FIG. 5, FIG. 5 is a functional block diagram of accessnode 104 a according to some embodiments of the invention. As shown,access node 104 a may comprise a data processing system 502 (e.g., oneor more microprocessors, one or more integrated circuits, and/or one ormore circuits for processing data), a data storage system 506 (e.g., oneor more non-volatile and/or volatile storage devices) and computersoftware 508 stored on the storage system 506. Configuration parameters510 may also be stored in storage system 506. Access node 104 a alsoincludes transmit/receive (Tx/Rx) circuitry 505 for transmitting data toand receiving data from UEs 102 and transmit/receive (Tx/Rx) circuitry504 for transmitting data to and receiving data from, for example,network 110. Software 508 is configured such that when data processingsystem 502 executes software 508, access node 104 a performs stepsdescribed above (e.g. steps described above with reference to the flowchart shown in FIGS. 3 and 4). For example, software 508 may include:(1) computer instructions for determining the load in a cell, (2)computer instructions for setting a CPI value based on the determinedcell load, (3) computer instructions for including the CPI value in amessage, and (4) computer instructions for transmitting (e.g.broadcasting or unicasting) the message.

Referring now to FIG. 6, FIG. 6 is a functional block diagram of a UE102 according to some embodiments of the invention. As shown, UE 102 maycomprise a data processing system 602 (e.g., one or moremicroprocessors, one or more integrated circuits, and/or one or morecircuits for processing data), a data storage system 606 (e.g., one ormore non-volatile and/or volatile storage devices) and computer software608 stored on the storage system 606. Configuration parameters 610 (e.g.the above described timer intervals) may also be stored in storagesystem 606. UE 102 also includes transmit/receive (Tx/Rx) circuitry 604for transmitting data to and receiving data from an access node.Software 608 is configured such that when processor 602 executessoftware 608, UE 102 performs steps described above (e.g. stepsdescribed above with reference to the flow chart shown in FIG. 2). Forexample, software 608 may include computer instructions for executing acell selection rule using a CPI value received from the access node.

While various embodiments of the present invention have been describedabove, it should be understood that they have been presented by way ofexample only, and not limitation. Thus, the breadth and scope of thepresent invention should not be limited by any of the above-describedexemplary embodiments.

Additionally, while the processes described above and illustrated in thedrawings are shown as a sequence of steps, this was done solely for thesake of illustration. Accordingly, it is contemplated that some stepsmay be added, some steps may be omitted, the order of the steps may bere-arranged, and some steps may be performed in parallel.

The invention claimed is:
 1. A method for load balancing in a userequipment (UE), the method comprising: receiving at a UE a messagecomprising a cell selection rule, wherein the cell selection rulecomprises: a selection condition, wherein the selection conditionindicates one or more conditions under which the cell selection rule isto be applied; and a selection instruction, wherein the selectioninstruction indicates an order of cells; receiving at the UE a cellpreference indicator (CPI) value transmitted from an access node,wherein the CPI value indicates a load associated with a first cell;determining, based on the received CPI value, whether the selectioncondition is satisfied; in response to determining the selectioncondition is satisfied, selecting one of the first cell and a secondcell based on the order indicated by the selection instruction; andconnecting to the selected cell.
 2. The method of claim 1, wherein theCPI value is a binary load indicator value that indicates whether thefirst cell is considered to be loaded or unloaded.
 3. The method ofclaim 1, wherein the CPI value is a load indicator value that indicatesone of three or more cell load levels.
 4. The method of claim 1, whereindetermining, based on the received CPI value, whether the selectioncondition is satisfied comprises generating a random or pseudo-randomnumber and comparing the generated number with a value that is afunction of the CPI value.
 5. The method of claim 1, wherein: the accessnode is a 3GPP access node, and the second cell is serviced by a secondaccess node that is not a 3GPP access node.
 6. The method of claim 1,wherein receiving the CPI value comprises receiving a message broadcastfrom the access node on a broadcast channel (BCH) or a downlink sharedchannel (DL-SCH) or unicast from the access node, wherein the messageincludes the CPI value.
 7. The method of claim 1, further comprising:setting a timer; and in response to the expiration of the timer,determining, based on a default CPI value whether to utilize the secondcell.
 8. The method of claim 1, further comprising: setting a timer ifthe first cell was selected; and in response to the expiration of thetimer, determining, based on the received CPI value or a new CPI value,whether to continue utilizing the first cell.
 9. A communicationapparatus, comprising: a transmit and receive circuit operable to:receive a message comprising a cell selection rule, wherein the cellselection rule comprises: a selection condition, wherein the selectioncondition indicates one or more conditions under which the cellselection rule is to be applied; and a selection instruction, whereinthe selection instruction indicates an order of cells; receive a cellpreference indicator (CPI) value transmitted from an access node,wherein the CPI value indicates a load associated with a first cell; anda data processing system configured to: determine, based on the receivedCPI value, whether the selection condition is satisfied; in response todetermining the selection condition is satisfied, select one of thefirst cell and a second cell based on the order indicated by theselection instruction; and connect to the selected cell.
 10. Thecommunication apparatus of claim 9, wherein the CPI value is a binaryload indicator value that indicates whether the first cell is consideredto be loaded or unloaded.
 11. The communication apparatus of claim 9,wherein the CPI value is a load indicator value that indicates one ofthree or more cell load levels.
 12. The communication apparatus of claim9, wherein the data processing system is configured to determine whetherthe selection condition is satisfied by generating a random orpseudo-random number and comparing the generated number with a valuethat is a function of the CPI value.
 13. The communication apparatus ofclaim 9, wherein: the access node comprises a 3GPP access node, and thesecond cell is serviced by a second access node that is not a 3GPPaccess node.
 14. The communication apparatus of claim 9, wherein thetransmit and receive circuit is configured to receive the CPI value byreceiving a message broadcast from the access node on a broadcastchannel (BCH) or a downlink shared channel (DL-SCH) or a unicast fromthe access node, wherein the message includes the CPI value.
 15. Thecommunication apparatus of claim 9, wherein the data processing systemis further configured to: set a timer; and in response to the expirationof the timer, determine, based on a default CPI value whether to utilizethe second cell.
 16. The communication apparatus of claim 9, wherein thedata processing system is further configured to: set a timer if thefirst cell was selected; and in response to the expiration of the timer,determine, based on the received CPI value or a new CPI value, whetherto continue utilizing the first cell.